Culm Facies Research Articles

Comparative geochemistry of Early Carboniferous marine red beds (MRBs) and their significance for deep time paleoceanographic reconstructions

Marine red beds (MRBs), also known as oceanic red beds (ORBs), are reddish colored sediments deposited within the marine realm that have been stained during deposition and/or early diagenesis because of changes in the ocean water chemistry in response to paleoceanographic and paleoclimatological factors. Although common throughout the Phanerozoic, marine red beds have mostly been investigated in Upper Cretaceous successions as CORBs (Cretaceous Oceanic Red Beds) - their occurrence and paleoceanographic context within the Paleozoic has yet to be studied in detail. Here we describe and interpret the high-resolution litho- and chemofacies of Early Carboniferous (Late Viséan) marine red beds from the northern coast of Menorca (Balearic Islands, Spain) that mark a rapid transition from siliceous radiolarian chert deposition to re-worked carbonate debrites followed by typical European Culm facies. The succession was deposited within a strait-like narrow basin that formed part of the Alboran-Kabylian-Peloritan-Calabrian terrane in the Western Paleotethys Ocean prior to the onset of the Variscan Orogeny. The marine red bed geochemistry is described in terms of three geochemical endmembers Al-MRBs (clayey), Ca-MRBs (calcareous) and Si-MRBs (siliceous) by using XRF-derived Al2O3, CaO, and SiO2 concentrations. This study finds that Viséan marine red beds from Menorca are predominantly Al-MRBs with subordinate Ca-MRBs. Furthermore, we compare the bulk rock geochemistry of the Viséan marine red beds of this study with the geochemical data of Paleozoic, Mesozoic and Cenozoic marine red beds available in the existing literature (Cambrian, Silurian, Jurassic, Cretaceous, Paleogene and recent Pacific Ocean red clays) to highlight the significance of marine red bed occurrences in relation to (paleo-)bioproductivity fluctuations, deep-water oxygenation and oceanic redox transitions. This study finds that Phanerozoic marine red beds are dominantly Al-MRBs and Ca-MRBs, whilst Si-MRBs are less common. The Early Carboniferous marine red beds of the present study were formed in a distal, deeper-marine environment under oxic-suboxic, oligotrophic conditions. A lack of any significant Fe2O3T enrichment points towards a more complex diagenetic process for the origin of the red color imparted in Phanerozoic MRBs.

The first lower Viséan trilobite association from limestone facies of the Moravian Karst and its relation to the sedimentary environment (Líšeň Formation, Czech Republic)

A lower Visean trilobite association from limestones of the Liseň Formation in the Moravian Karst (Czech Republic) was studied in detail for the first time. The trilobites were obtained from a thin interval in the succession of the HadyŘicka Limestone exposed in the Zetor section situated on the southern margin of the Moravian Karst near Brno. The limestone succession of the Zetor section with prevalently distal calciturbidites was deposited on the lower part of the carbonate ramp. Biostratigraphic data suggest the span of the lower Visean MFZ11 (foraminiferal zone) for the interval rich in trilobites. The trilobites are preserved in at least a partly silicified state. Around twenty trilobite species or subspecies were recorded including one new taxon Bollandia megaira brunensis subsp. nov., various species of ?Namuropyge R. Richter & E. Richter, Liobole R. Richter & E. Richter, Angustibole G. Hahn, ?Cyrtoproetus Reed, Gitarra Gandl, Pseudowaribole (Geigibole) Gandl, Winterbergia G. Hahn & Brauckmann, Bollandia Reed and several taxa of problematic affinity, which are discussed. The recorded taxa show an affinity with associations from the Erdbach Limestone facies in Germany but also with other areas (e.g. Cantabrian Mountains, Spain). The trilobite association shows similarities to the “Shelf Slope” and “Erdbacher Kalke” communities recorded in Germany. In contrast, the previously described lower Visean trilobite associations from the Moravian Karst were restricted to the aleuropelitic facies of the Březina Formation and correspond rather to the “Culm facies” community known from Germany. These associations might represent more distal and deeper basinal settings than the Zetor section or an environment of generally similar depths with a different source area and bottom topography.

Segmentichnus mohri igen. et isp. nov., a giant new trace fossil from the Culm facies (lower Carboniferous) of the Franconian Forest (Saxothuringian Belt, Germany)

A new ichnogenus and ichnospecies, Segmentichnus mohri, is recognized in the lower Carboniferous deep-sea Culm facies deposits in the southern Germany. The trace fossil is an unusually large, horizontal, tubular burrow with primary successive branching and transverse annulation with ring-like, slightly irregular swellings, without wall, preserved in full relief in dark grey slate. Segmentichnus mohri is interpreted to be a locomotion and feeding trace (pascichnion) produced within the mud by unknown ‘worm’-like animal in a turbiditic depositional system. It belongs to the transition between the Paleodictyon and Nereites ichnosubfacies of the Nereites ichnofacies.

Trace fossils from the Mississippian of the Piaskowa Góra section (the Intra-Sudetic Basin, SW Poland)

Eight ichnotaxa and enigmatic tubular forms were discovered and described for the first time from clastic deposits (the Culm facies) of the uppermost part of the Szczawno Formation (upper Mississippian) from in the Piaskowa Góra section in the northern part of the Intra-Sudetic Basin near Wałbrzych. The trace fossils are represented mostly by pascichnia and less numerous domichnia, fodinichnia and repichnia. Psammichnites plummeri and numerous Phycosiphon isp . are the most common ichnotaxa. They are accompanied by Archaeonassa fossulata, Beaconites cf. capronus , Curvolithus multiplex, Dictyodora liebeana, Palaeophycus isp ., and Planolites isp . D. liebeana is described for the first time from the lower Serpukhovian. Most components of the ichnoassemblage are typical of the Cruziana ichnofacies, but the co-occurrence of Dictyodora and Phycosiphon could indicate a transition to deeper environmental settings (the Zoophycos ichnofacies). The lithological features as well as the accompanying trace fossils, wrinkle structures and floral remains of Archaeocalamites indicate rapid sedimentation, alternating with more tranquil periods of sedimentation, in an intermediate environment between the lower offshore (the distal Cruziana ichnofacies) and the fan-delta slope (below the wave base, the Zoophycos ichnofacies). The studied trace fossils and palynological data indicate that marine conditions in the Wałbrzych area in the Mississippian prevailed locally until the early Sepukhovian.

Thermal parameters of roofing slates from Czech Republic

Thermal performance of building materials is an important parameter from the point of view of energy consumption for heating buildings, which is obviously related to environmental protection standards. Thermal parameters of roofing slates were measured for samples from two different formations in the Czech Republic. These were rocks of lower Carboniferous Culm facies of Moravice Formation and Silesian Unit of Flysch Moravian-Silesian Carpathians. Thermal conductivity and thermal effusivity measurements were performed with use of TCi analyser. Thermal parameters were obtained in parallel and perpendicular direction to the bedding in rocks. Thermal conductivity of the Moravian slates in the direction perpendicular to the bedding ranges from 1.43 to 1.79 W m−1 K−1, while for samples from Carpathian region this parameter ranges from 1.99 to 3.15 W m−1 K−1. High values of thermal conductivity correlate to higher quartz content in the rocks. The measured thermal parameters (conductivity, effusivity, diffusivity) are strongly depending on the direction of measurement. Thermal conductivity of analysed rocks increases along with increase in temperature. The increase in thermal conductivity value is more significant in case of Moravian slates. In practice, the obtained results indicate that the traditional building material, such as roofing slates, shows better insulation properties at lower temperatures, while in conditions of strong sunlight the temperature conductivity increases. In case of roofing slates, which tend to be highly anisotropic, the essential information is the direction of thermal parameters measurement. Slates, due to their specific texture, are characterized by a very high thermal anisotropy coefficient.

The radioisotopically constrained Viséan onset of turbidites in the Moravian-Silesian part of the Rhenohercynian foreland basin (Central European Variscides)

The Březina Formation represents the initiation of siliciclastic flysch turbidite sedimentation at the eastern margin of Bohemian Massif or within the Rhenohercynian foreland basin. Its deposition started after drowning of the Devonian carbonate platform during Visean (Mississippian) times, resulting in a significant interval of black siliceous shale and variegated fossiliferous shale deposition in a starved basin. Near the top of the Březina Formation an acidic volcanoclastic layer (tuff) of rhyolitic composition has been dated with high precision U–Pb zircon chemical abrasion isotope dilution method at 337.73 ± 0.16 Ma. This new radiometric age correlates with the previously inferred stratigraphic age of the locality and the current calibration of the Early Carboniferous geologic time scale. Shales of the Březina Formation pass gradually upwards into the siliciclastics of the Rozstani Formation of the Drahany culm facies. Thus our new age offers one of the few available radioisotopic constraints on the time of onset of siliciclastic flysch turbidites in the Rhenohercynian foreland basin of the European Variscides.

ICHNOFOSILIE MYSLEJOVICKÉHO SOUVRSTVÍ DRAHANSKÉHO KULMU (SPODNÍ KARBON, MORAVSKOSLEZSKÁ JEDNOTKA ČESKÉHO MASIVU)

The research in this study is focused on trace fossils of the Myslejovice Formation, which is one of the lithostratigraphical units in the Lower Carboniferous sequences of the Drahany Culm Basin that belongs to the large area of Rhenohercynian Zone of the Variscan orogenetic flysch belt. Ichnofossils have mainly been collected in the southeastern part, near Vyškov. The material comes from the collection of Mr. Veleslav Lang which is nowadays stored in the Regional Museum of Olomouc. From this collection total 615 specimens in 10 ichnogenera and 13 following ichnospecies were determined and redefi ned: ?Alcyonidiopsis isp., Cosmorhaphe isp., Dictyodora liebeana, Diplocraterion parallelum, Gordia isp., Chondrites cf. intricatus, Chondrites isp., Nereites missouriensis, Nereites isp., Phycosiphon incertum, Planolites beverleyensis, Planolites isp. and Rhizocorallium isp. The revised material comes from the following locations: Opatovice, Habrovany, Hamiltony, Ježkovice, Lhota, Luleč, Myslejovice, Nemojany – Blatická dolina, Nemojany, Otaslavice, Pístovice, Radslavice and Rychtářov. The overall character of ichnoassemblages indicates conditions of Nereites ichnofacies, which is typical for the distal parts of the suprafan turbidite lobes. Compared to other areas of Culm facies in Middle Europe, assemblages of the Myslejovice Formation belong among the less diversified.

Mineral-forming and diagenetic processes related to Tertiary hydrocarbon seepage at the Bohemian Massif/Outer Western Carpathians interface: Evidence from the Hrabůvka quarry, Moravia, Czech Republic

Ancient hydrocarbon seepage occurred in the Hrabůvka quarry at the boundary between the basement of the Bohemian Massif (represented by folded Lower Carboniferous siliciclastics of the Culm facies) and Tertiary sedimentary cover of the Carpathian Foredeep (formed by Lower Badenian siliciclastics and calcareous clays). The unconsolidated Lower Badenian sediments contain lithified domains composed of limestone and breccias with limestone cement, whereas the basement rocks are cut by subvertical neptunic dykes filled up by limestone and calcite-marcasite-pyrite veinlets representing sealed fluid conduits. The deeply negative δ13C values of both vein calcite and limestone (down to −38.1‰ V-PDB) indicate that oxidation of hydrocarbons was the major source of carbon for authigenic mineralization. A fluid inclusion study suggests low fluid temperatures (<50 °C) and low and variable salinities of aqueous fluids associated with hydrocarbons (0.7–6.7 wt. % NaCl eq.). The variability of δ18O values of authigenic carbonates (−1.7 to −8.2‰ V-PDB) could reflect either slight changes in temperature of escaping fluids (mostly within 15 °C), and/or some mixing with meteoric waters. The low δ34S values of vein marcasite (∼–20‰ V-CDT) are consistent with bacterial reduction of sulfate in the hydrothermal system. Low C1/(C2+C3) ratios in hydrocarbon gas extracted from authigenic carbonates (9.9 and 5.8) as well as the high δ13C values of methane (−31.8 and −32.4‰ V-PDB) are compatible with a thermogenic source of hydrocarbons. REE data indicate sequestration of REE from finely dispersed detrital material in the apical part of the hydrothermal system. The available data are compatible with two possible scenarios of fluid origin. The hydrocarbons could have been leached from underlying Paleozoic sedimentary sequence by aqueous fluids that infiltrated into the basement after Tertiary tectonic reactivation. Alternatively, an external source of hydrocarbon-bearing fluids can be found in the adjacent Outer Western Carpathians flysch nappes containing petroleum-producing lithologies. Nevertheless, a regional flow of hydrocarbon-bearing fluids is evidenced by the occurrence of very similar hydrocarbon-bearing vein mineralizations in a wider area.

Biostratigraphic zonation and correlation of Mississippian rocks in Western Europe: some case studies in the late Viséan/Serpukhovian

AbstractIn the Mississippian in Western Europe, biostratigraphic zonation and correlation of sequences has been refined using a combination of faunal and floral groups. In deep‐water basins and on shelves advances have been made in recognizing evolutionary lineages of conodonts, particularly in the early Viséan to Serpukhovian, for example the Gnathodus praebilineatus ‐ G. bilineatus bilineatus ‐ G. bilineatus bollandensis lineage, which is closely tied to ammonoid zones in the Culm facies of Western and Central Europe, and the Lochriea saharae ‐ L. commutata ‐ L. nodosa ‐ L. ziegleri lineage. Moreover, progress has been made in recognizing the Upper Viséan/Serpukhovian boundary, based on the first appearance datum (FAD) of Lochriea ziegleri.Greater precision in the dating and correlation of shallow‐water platform facies has been achieved using foraminiferans. Although evolutionary developments in the Archaediscidae are still of major importance in terms of biostratigraphic dating, alternative lineages have been proposed recently for the late Asbian/Brigantian (late Viséan) interval, involving the Cribrospira ‐ Bradyina ‐ Parajanischewskina ‐ Janischewskina lineage. These large cribrate complexed‐walled forms are widely recognized throughout Western Europe. The base of the Viséan has recently been defined in South China using foraminiferans with the FAD of Eoparastaffella simplex in the lineage Eoparastaffella ovalis ‐ E. simplex. The same criterion has been used to define the base of the Viséan (base of emended Moliniacian) in Belgium.Recent studies in Britain, Ireland, France, Spain and Poland have demonstrated that in the Upper Viséan many calcareous algal taxa and problematica are widespread in their distribution throughout the western Palaeotethys Realm. Moreover, five algal assemblages can be distinguished, based either on the first appearance of certain taxa or their acme developments, such as Falsocalcifolium punctatum and Calcifolium okense. In addition, there have been new discoveries in the Brigantian and Serpukhovian of algal taxa and problematica such as Archaeolithophyllum, Paraepimastopora and Claracrusta that were regarded previously as being restricted to the Pennsylvanian‐Permian interval.Advances in rugose coral biostratigraphy have also been made in the upper Tournaisian and Upper Viséan, particularly using dissepimented taxa which occur in shallow‐water platforms. The presence of uraliniids and Keyserlingophyllum in the upper Tournaisian of Western Europe (Belgium) are also recognized in South China and Siberia. In the Upper Viséan, refinements in zonation have been made using well‐defined colonial and solitary species and species groups belonging to the families Lithostrotionidae and Axophyllidae and solitary taxa of the families Aulophyllidae and Cyathopsidae which are recognized throughout the western Palaeotethys. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Silurian to Mississippian series of the eastern Catalan Pyrenees (Spain), updated by conodonts, foraminifers and algae

Stratigraphic sections and microfossils samples from the upper part of the “Graptolitic Shales- Orthoceras Limestones” and from the Camprodon Formation lying in the area of Camprodon, eastern Pyrenees, Spain, have been studied. Some beds at the top of the “Graptolitic Shales- Orthoceras Limestones” correspond to the Torres Member of the Rueda Formation, and conodont faunas, indicating a Lochkovian age, are described. The Camprodon Fm. is interpreted to be turbidites deposited in deep sea fans, although slope deposits prevail in the eastern sections. One reworked carbonate clast from the Camprodon Fm. provided a valuable early Ludlow conodont fauna, from the Kockelella crassa Zone, reported for the first time in the Iberian Peninsula. Late Devonian conodonts and late Visean (Asbian-Brigantian) foraminifers and algae were also obtained from reworked limestone clasts, and latest Visean or Serpukhovian foraminifers from the sandstone matrix in the Camprodon Fm. The studied microfossils suggest a late Mississippian age for the Camprodon Fm. instead of the previously assigned late Silurian-Lochkovian age. This age must be considered when discussing the distribution of the Culm Facies in the Pyrenees and the significance of the contact between the Camprodon Fm. and the underlying “Graptolitic Shales”.

Combined tectonic-sediment supply-driven cycles in a Lower Carboniferous deep-marine foreland basin, Moravice Formation, Czech Republic

The Lower Carboniferous Moravian–Silesian Culm Basin (MSCB) represents the easternmost part of the Rhenohercynian system of collision-related, deep-water foreland basins (Culm facies). The Upper Visean Moravice Formation (MF) of the MSCB shows a distinct cyclic stratigraphic arrangement. Two major asymmetric megacycles bounded by basal sequence boundary, each about 500 to 900 m thick, have been revealed. The megacycles start with 50- to 250-m-thick, basal segments of erosive channels: overbank successions and slope apron deposits interpreted as lowstand turbidite systems. Up-section they pass into hundred metre-thick, fine-grained, low-efficiency turbidite systems. Palaeocurrent data show two prominent directions, basin axis-parallel, SSW–NNE directions, which are abundant in the whole MF, and basin axis-perpendicular to oblique, W–E to NW–SE directions, which tend to be confined to the basal parts of the megacycles or channel-lobe transition systems in their upper parts. Based on the facies characteristics, palaeocurrent data, sandstone composition data and trace-fossil distribution data, we suggest a combined tectonics–sediment supply-driven model for the MF basin fill. Periods of increased tectonic activity resulted in slope oversteepening probably combined with increased rate of lateral W–E sediment supply into the basin, producing the basal sequence boundary and the subsequent lowstand turbidite systems. During subsequent periods of tectonic quiescence, the system was filled mainly from a distant southern point source, producing the thick, low efficiency turbidite systems. Consistently with the previous models, our own sediment composition data indicate a progressively increasing sediment input from high-grade metamorphic and magmatic sources up-section, most probably related to an uplift in the source area and progressive unroofing of its structurally deeper crustal parts. The first occurrence of the Cruziana–Nereites ichnofacies in sand-rich turbidite systems in the youngest parts of the MF (Goβel to Goβspi Zone), supported by rapidly increasing quartz concentrations in sandstones, is thought to indicate a transition from generally underfilled to generally overfilled phase in evolution of the MSCB basin. This transition may be linked to the onset of Upper Visean phase of northward basin-fill progradation assumed by previous authors.

Stratigraphy of Lower Cambrian and unconformable Lower Carboniferous beds from the Valls unit (Catalonian Coastal Ranges)

The Palaeozoic rocks outcropping around Valls are divided into two stratigraphic units. The boundary between both is an unconformity. The lower unit is composed by nearshore platform sediments and a Lower Cambrian age is indicated according to ichnotaxa content. The upper unit consists of pink nodular limestones and dark limestones, and it is followed by siliciclastic Culm Facies rocks. These limestones contain conodonts of the Uppermost Tournaisian at its base (anchoralis-latus Zone) and Lower Bashkirian (Namurian B) in the upper part. This condensed carbonate sequence was coeval with the thick siliciclastic Culm sedimentation in the surrounding areas.

Tabulés dinantiens du Sud-Ouest du Portugal [Tabulate corals from the Dinantian of South-Western Portugal

A small fauna of Tabulate corals, collected in the Visean of South-Western Portugal (Carrapateira-Bordeira area), is systematically described. The genera Sutherlandia Cocke &amp; Bowsher 1968, Smythina Weyer 1970 and Cladochonus McCoy 1847 are for the first time reported from the Dinantian of Portugal. A similar association is known from the Culm facies of England and Germany. That confirms the close affinities between these regions and Portugal in the early Carboniferous. The growth habits of the corals suggest that the community was living on a soft muddy bottom. A comparison is proposed with the classical Tabulate coral fauna of Basleo, in the Permian of Timor.

Postvolcanic Paleozoic of the Iberian Pyrite Belt: An Example of Basin Morphologic Control on Sediment Distribution in a Turbidite Basin

ABSTRACT The Iberian Pyrite Belt (South Portuguese Zone, Hercynian Chain), an important metallogenic province, has a volcanic-sedimentary origin. Overlying this volcanic succession is a thick sedimentary unit, the Culm Group, which represents postvolcanic Paleozoic sediments of the Iberian Pyrite Belt. It consists of three stratigraphic units: the Basal Shaly Formation (BSF), the Culm Facies Turbiditic Formation (CFTF), and the Shallow-platform Sandy Unit (SPSU). The BSF is represented by finegrained sediments of volcanic to nonvolcanic origin that mark the end of volcanism in the region, the reworking of volcanic products in a shallow-marine basin, and the beginning of autochthonous sedimentation of pelagic clay. It constitutes a depositional sequence sensu Mitchum et al. (1977). The d stribution, facies, and facies associations of the turbidites of the CFTF are related to the configuration of the basin, which controlled the mechanisms of deposition and distribution of the detritus from different source areas. The SPSU represents sediments eroded from the volcanic upland and redistributed over the shelf. Detailed study of these three units and their relationships provides the means to define the geometry and evolution of the postvolcanic Carboniferous basin of the Iberian Pyrite Belt. The basin was roughly subdivided by the Paymogo and the Puebla de Guzman paleoridges. Together with the allochthonous Ossa-Morena Zone, north of the study area, they formed three topographic barriers that delineated two interconnected subbasins. Sedimentation in the postvolcanic basin of the Iberian Pyrite Belt can be related to a model of oscillating sea level. Synorogenic characteristics of the Culm Group sediments support a tectonic origin for the sea-level oscillations, particularly since the sediments had already been affected by the first pulses of the Hercynian Orogeny.

Dispositivos turbidíticos sincrónicos en el Carbonífero Inferior de la Faja Piritica Iberica (zona Sur-Portuguesa)

This paper deals with the stratigraphy and sedimentology of the Culm facies in a sector of the Iberian Pyrite Belt (South-Portuguese Zone). In the studied area two main turbidite systems occur. The WNW-ESE one is made with turbidites of type I and III (Mutti, 1985), the other one, with a direction NE-SW, includes turbidites of type 11 and 111. The contemporary interrelation between the two main turbidite systems suggests a catastrophic way of deposition for this sediments. This Gibraleon area is interpreted as the place where this interrelation occur, their facies cycles including intermediate characteristic of the two systems.

Was the Hercynian Orogenic Belt of Europe of the Andean Type ?

THE Hercynian orogenic belt has distinctive features with regard to the preceding and subsequent orogenies, as demonstrated by Zwart1 and others2. It appears to have formed on a continental basement. There is no evidence for a large eugeosyncline, but rather small subsiding basins or troughs with a shallow type of sedimentation. It is characterized by clastic volcano-sedimentary formations often represented in the Culm facies, pointing to a chiefly submarine or aerial intermediate and acid volcanism of explosive style. From North Britain to the Urals, they form an almost continuous belt (Fig. 1). which could have been a line of volcanic eruptions, active from late Devonian till the end of the lower Carboniferous. The syn- or post-tectonic magmatism is emphasized by intensive granitization (granites and granodiorites) which are, in turn, followed by rhyolitic volcanism during the Permian. The Hercynian metamorphism is rather weak, usually covering the green schist facies and reaching locally the amphibolite facies in the low pressure high temperature series. The tectonic style as it is best observed in the external northward zones appears to be the result of weak compressions and, in contrast, of block faulting which might be partially responsible for passive shear folding in the sedimentary cover, with axial planes parallel to the faults in the basement.

Dolnokarbońska facja kulmowa w podłożu zapadliska przedkarpackiego

LOWER CARBONIFEROUS CULM FACIES IN SUBSTRATUM OF THE CARPATHIAN FORE-DEEP Amidst the ten bore-holes, in which the Carboniferous was encountered in the substratum of the Carpathian Fore-deep. Southern Poland, the most interesting is bore-hole Podborze 10 completed in 1959-1960. The Carboniferous deposits discovered in this bore-hole are developed mostly in the Culm facies, hitherto not known within the substratum of the unit discussed in the paper. The sediments were pierced at the depth from 2326,00 to 2718,00; they Occur beneath the Zechstein, and on the Precambrian deposits. At the bottom, they are represented by fine-grained sandstones and limestones (data only from fragmental samples), rich in ,detritus of crinoids brachiopods and ostracods, as well as by a thick series of . dark-grey; clayey, locally clayey-siliceous shales with interbeddings of siltstones .and sandstones. At its top part the series is often cherry-red in colour, lacks fauna, but contains flora and thin interbeddings of strongly squeezed claystones.

A MID-CARBONIFEROUS UNCONFORMITY IN THE SKIPTON ANTICLINE

From Skipton to Bolton Abbey, Carboniferous rocks are broadly folded into an anticline known as the Skipton Anticline. The greater part of the succession exposed in the anticline is mainly composed of dark-grey argillaceous limestones and shales, a Carboniferous facies usually referred to as the Culm facies. These beds are of Lower Carboniferous (Dinantian) age. The upper beds exposed on the flanks of the anticline are mainly felspathic sandstones and shales of Millstone Grit facies and Namurian in age. At three levels in the Dinantian, the rocks are limestones with little or no shale. These limestones are fossili-ferous and their position in the Lower Carboniferous zonal sequence with an estimate of their very variable thickness was given in 1926, as follows[*][1]:— | Namurian | { | | Basement Grits | | | || | E1 | Upper Bolland Shales | } | 700 ft. | | Dinantian | { | P | Lower Bolland Shales | | | D1 | Eastby Limestone | | 250 ft. | | | Shales with Limestone | | 1400 ft. | | S | Embsay Limestone | | 400ft. | | | Shales with Limestone | | 1600 ft. | | C | Haw Bank Limestone | | 800 ft.+ | The Skipton-Bolton Abbey area is part of the Craven Lowland basin of sedimentation which existed in Dinantian and Namurian times south of the Craven Highland massif. As the rocks of the Skipton anticline are almost entirely of Culm facies, the area has therefore been considered as part of a mid-basin facies belt, one of the series of facies-belts into which the Craven Lowlands have been divided.[†][2] In no part of the succession of the Skipton anticline is there any development of reef limestone, characteristic of a marginal facies belt. Whereas … [1]: #fn-1 [2]: #fn-2